Field of the Invention
The current invention relates to a hydraulic advancing support frame with a lifting cylinder to raise base shoes during the advancing process.
The mining of coal seams is carried out by an alternating sequence of winning coal using a mining machine, which is driven along the coal front on a face conveyor, and supporting the roof thereby exposed by hydraulic advancing support frames brought up on the goaf side of the conveyor, which follow the conveyor and move forward by steps onto the exposed cut floor of the seam. This process assumes an essentially even floor. Unevenness in the floor caused by the geology and soft ground rock can substantially hinder the stepping process, since the floor shoes come up against steps or sink into the ground. For these reasons lifting arrangements are employed, by which the forward ends of the base shoes are raised during the movement process.
An advancing support frame comprises as its main components base shoes, hydraulic props to support a roof canopy and a gob shield as well as an advancing arrangement with an advancing cylinder, which joins the support to the face conveyor at the mining face. The advancing cylinder is arranged between the base shoes of the powered support assembly and engages with the piston rod extending towards the goaf side on an advancing rod which is linked to the conveyor on the face side. A lifting cylinder to even out differences of level between the conveyor and the base shoes is mounted in an upright position on the base shoes and at its free end is supported with the extending piston rod on the advancing rod. During mining the lifting cylinder slides over the advancing rod which moves forward with the conveyor. The cylinder is lifted by upwards pivoting movements of the advancing rod on travelling over unevennesses in the ground, whereby the lifting cylinder is pushed in. During the process of advancing the lifting cylinder raises the forward ends of the base shoes and brings them again to the level of the advancing rod. In the same way the lifting cylinder prevents the tips of the base shoes from digging into soft ground.